Devices for providing liquid, for example brewing liquid, which encompass a water tank, which serves as buffer storage and which is connected directly to a water connection by means of a water inlet, in particular to the potable water supply, or which is connected in intervals, respectively, are used in the semi-gastronomy and gastronomy field in beverage machines, in particular in coffee machines or coffee dispensers. By providing such a “fixed mains water supply”, which can be controlled in intervals, fresh water can always be held available in the water tank, for example, for preparing a coffee beverage, which reduces possible compromise of taste due to stagnant water.
Devices for providing liquid for a beverage machine having a water tank, which can be connected directly to the potable water supply, which are known from the technical background, are hereby commonly provided with a working float switch or other sensor devices, which, when filling or refilling the water tank, respectively, via the fixed mains water supply, close a inlet valve, which is installed in the path between water connection and water inlet, by means of a reed switch, when a target water level has been reached, by interconnecting a suitable control device.
Document U.S. Pat. No. 6,401,729 B1 discloses a device for flushing or for cleaning reservoirs, in which beverages, such as coffee, tea or concentrated beverages are stored, wherein this device is to be suitable to be able to simultaneously flush two such reservoirs for beverages. The device known from U.S. Pat. No. 6,401,729 B1 encompasses a water tank (96) having at least one water inlet (104) for filling the water tank (96), which is connected to a water connection (100) via a valve (102). The water inlet (104) can be controlled via the valve (102) with the help of a control device (94). The control device fills the water tank (96) with pressurized water until a filling level sensor (106) outputs a signal, according to which the water tank (96) has reached or exceeded its first, that is, full, liquid filling level. For this purpose, the filling level sensor (106) is connected to the control device (94) electronically. This control device (94) is also designed to control the water inlet according to the signal of the at least one filling level sensor (106). According to U.S. Pat. No. 6,401,729 B1, the flushing water located in the water tank (96) is guided to a spray head (114) via an output line (108) as soon as a metering valve (100) is opened by means of the control device (94). The spray water is then introduced into the holder (20) via the spray head (114), whereby a brewing process is initiated, which will not be explained in detail herein. Even though U.S. Pat. No. 6,401,729 B1 describes a cleaning process, but said cleaning process does not serve to clean the water tank (96), but to clean the beverage reservoirs 24 or 26, respectively, that is, a possibility for emptying or cleaning the water tank (96), respectively, is not described.
For example, a coffee machine having a water tank, which is embodied as buffer storage and which encompasses two water level sensors, which are connected to a control unit, is known from U.S. Pat. No. 5,063,836. The inlet valve between the fixed mains water supply and the inlet of the water tank, thus the water inlet, is hereby opened as long as the lower water level sensor does not report that the filling level, on the level of which it is attached inside the water tank, has been reached or exceeded. To prevent that, due to a defect of the water level sensor or, if applicable, also due to a contamination or calcification, the inlet valve remains opens for such a long time that the water tank runs over, a second water level sensor, which is to ensure a closing of the inlet valve by transmitting a corresponding signal to the control device, as soon as a water filling level has been reached, on the level of which this second upper sensor is attached, is arranged above the first water level sensor.
Such devices, which are known from the state of the art, have the disadvantage that cleaning, for example in the form of descaling, is difficult. In the case of the devices, which are known from the state of the art, it is thus not possible to fill a descaling liquid having a predetermined concentration into the water tank up to a level, at which a substantially complete cleaning or descaling, respectively, of all of the components arranged inside the water tank is ensured. In the case of the devices, which are known from the state of the art, it is furthermore not possible to remove a cleaning or descaling liquid, respectively, in a concentrated manner and substantially completely from the water tank once it has been added.